Having not been involved in any incidents myself, I must say that the displays are greatly appreciated and much part of the event, however echo that they have to be done safe, fireworks and booze don't mix very well (plus they don't light afterwards).
Have had experience of gas cylinders exploding vertically upwards on one occasion where some fool had lit an oil drum! The cylinder fortunately landed safely without harm, but some damage was done to surrounding tents by pieces of burning chicken carcass.
Moral, when you are going to burn stuff, try to predict all consequences.